Decreasing Ion-Diffusion Barrier Enables Superior Na-Ion Storage by Synergizing Hierarchical Architecture and Lattice Distortion.

Compared with nanosized materials, the long-pathway isolation of the interior part from the electrolyte for bulk electrode materials may result in high ionic diffusion barrier, leading to the poor rate behavior. Either the modification of lattice or the construction of a porous structure is generally effective to decrease the ion-diffusion barrier; however, achieving these multiscaled modulations simultaneously via a facile approach is still a challenge. Herein, we manipulate a bifunctional dopant to prepare micron-sized NaV(PO) with extraordinary synergy of hierarchical architecture and lattice distortion. The cations Zn not only substitute partial V to enhance the solid-phase ion diffusivity but also stabilize the lattice structure due to the pillar effect. Additionally, the anions CHCOO also participate in the reaction to modulate the porous architecture. The analysis results of galvanostatic intermittent titration technique, cyclic voltammetry, and electrochemical impedance spectroscopy demonstrate that the rational design of morphology and structure compounding lowers the ion-diffusion barrier and strengthens the Na migration kinetics. When evaluated as the cathode electrode, the optimal composite exhibits improved Na ion transport kinetics and superior rate behaviors of 72.2 and 58.7 mAh g at 100 and 200C, respectively.